The present invention relates to a new and improved construction of twin pusher centrifuge.
In its more specific aspects the present invention relates to a new and improved twin pusher centrifuge comprising a sieve or filter drum which is rotatable about its lengthwise axis at a predetermined rotational speed. The sieve or filter drum is provided with a product infeed and product discharge outlets or openings at both its opposite sides or ends. Approximately at the center or central region of the sieve or filter drum there is arranged a pushing device or pusher which is rotatable about the lengthwise axis of the sieve or filter drum at a rotational speed which is different from the rotational speed of such sieve or filter drum. The pusher serves to simultaneously convey the product which has been infed via the product infeed into the sieve or filter drum in the direction of both of the product discharge outlets or openings.
In a pusher centrifuge as known, for example, from U.S. Pat. No. 2,232,770, granted Feb. 25, 1941, a planar pusher or thrust floor member is mounted normally relative to the lengthwise axis of the sieve or filter drum and is periodically reciprocated in axial direction. Due to the oscillating reciprocation or to-and-fro movement of the pusher or thrust floor member the product which is infed via the product infeed close to the pusher floor member is periodically pushed in the direction towards the product discharge or outlet. Continuous operation of the centrifuge is thus possible. However, a complicated and expensive mechanical or hydraulic system is required for the periodic reciprocation of the pusher floor member. Considerable energy is consumed for displacing the masses which does not benefit the separating operation during centrifuging. Furthermore, the mass forces cause an unsteady or noisy operation of the centrifuge and exert a high load upon the bearings. Additionally, the movement of the pusher floor member in only one direction is utilized for pushing-out the product.
In a further construction of pusher centrifuge as known, for example, from U.S. Pat. No. 2,232,769, granted Feb. 25, 1941, the last-mentioned disadvantage is eliminated by arranging two sieve or filter drums so as to face each other on the side of their pusher floor members. A mechanical or hydraulic system is arranged between the two sieve or filter drums and simultaneously acts upon the two pusher floor members. The product contained in one sieve or filter drum is displaced in a direction towards the product discharge during one phase of the operation while the product contained in the other sieve or filter drum is displaced in a direction towards the product discharge during the other phase of the operation. However, the other disadvantages which are caused by the reciprocation of masses are equally not eliminated in this arrangement.
In a further development of such a pusher centrifuge as known, for example, from German Pat. No. 1,151,468, granted Feb. 6, 1964, a twin pusher centrifuge contains only one sieve or filter drum and a pusher floor member which is arranged at the center of the sieve or filter drum and which is reciprocated. Also, in this case the energy-consuming reciprocation of masses and an unsteady or noisy operation cannot be avoided. Further disadvantages of such prior art construction are that separate product infeeds are provided for the two sides of the pusher floor member. The infeed to the centrifuge thus is simultaneously effected on two opposite sides, however, by using separate infeeds which complicates the construction of the centrifuge and makes the same expensive. Additionally, it is not possible to ensure that the infeed of the product on the two sides always remains exactly the same, which creates disturbing asymmetries and requires an expensive regulation of the infeed of the product. Furthermore, it can be disadvantageous when processing certain products that the product has to be continuously infed, in order not to cause any return pressure shocks. In the case of certain products which are difficult to process, there thus exists the danger of flooding of the centrifuge if there are not available sufficiently long intermediate periods for separation of the fluid which is close to the pusher floor member and further product is continuously supplied.